Your friend is mistaken. This serial port he is talking about is called "CGA" and closely resembles a serial port. However it still requires a graphics card and a monitor! You can convert a CGA signal ...

[gmgfarrand] needed an extra USB port to power some devices. Since he just needed power, and no data, he slapped together this quick adapter that pulls power from the vga port instead. While we’re not ...

Simple question, yet oddly hard to google: Do they add any latency? Would performance be better than a DVI-D to VGA adapter? I know they have to have a DAC because DP doesn't natively output analogue.